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Beryllium oxide
| PubChem = 14775 | EINECS = 215-133-1 | RTECS = DS4025000 }} | Section2 = | Section7 = , , , , , | SPhrases = , | FlashPt = Non-flammable | LD50 = 2062 mg/kg (mouse, oral) }} | Section8 = }} Beryllium oxide (BeO) is a white crystalline oxide. It is notable as it is an electrical insulator with a thermal conductivity higher than any other non-metal except diamond, and actually exceeds that of some metals. Its high melting point leads to its use as a refractoryRaymond Aurelius Higgins, (2006), Materials for Engineers and Technicians, Newnes, ISBN 0750668504. It occurs in nature as the mineral bromellite. Historically beryllium oxide was called glucina or glucinium oxide. Preparation and Chemistry Beryllium oxide can be prepared by calcining (roasting) beryllium carbonate, dehydrating beryllium hydroxide or igniting the metal: :BeCO3→ BeO + CO2 :Be(OH)2 → BeO + H2O :2Be + O2 → 2BeO Igniting beryllium in air gives a mixture of BeO and the nitride Be3N2. Unlike oxides formed by the other group 2 (alkaline earth metals), beryllium oxide is amphoteric rather than basic. Beryllium oxide formed at high temperatures (>800°C) is inert but may be easily dissolved in hot aqueous ammonium bifluoride (NH4HF2) or a hot solution of concentrated sulfuric acid (H2SO4) and ammonium sulfate ((NH4)2SO4). Structure BeO at normal temperatures has the hexagonal wurtzite, form. This contrasts with other members of group 2, whose oxides, MgO, CaO, SrO, BaO have the cubic rock salt structure.. At high temperature the structure transforms to a tetragonal form. Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications ISBN 0-19-855370-6 . BeO is a unique metallic compound in that it is a non-ionic oxide. Applications Sintered beryllium oxide, which is very stable, has ceramic characteristics. Beryllium oxide is used for rocket engines, catalysts, semiconductors, moderators of atomic reactors, and neutron reflectors. Beryllium oxide is used in many high-performance semiconductor parts for applications such as radio equipment because it has good thermal conductivity while also being a good electrical insulator. It is used as a filler in some thermal interface materials such as thermal grease. Some power semiconductor devices have used beryllium oxide ceramic between the silicon chip and the metal mounting base of the package in order to achieve a lower value of thermal resistance than for a similar construction made with aluminium oxide. It is also used as a structural ceramic for high-performance microwave devices, vacuum tubes, magnetrons, and gas lasers. Currently there are only two companies in the United States that manufacture Beryllium Oxide which are American Beryllia Inc. of Haskell New Jersey, and Brush Ceramics of Tucson Arizona. Safety BeO powder is carcinogenic if the powder is ingested or inhaled and may cause chronic beryllium disease. However, once fired into solid form, it is safe to handle as long as it is not subjected to any machining that creates dust.http://www.americanberyllia.com/safety.html Beryllium oxide ceramic is not a hazardous waste under Federal law and its use is not banned, restricted or otherwise limited by any country worldwide. References External links *Beryllium Oxide MSDS from American Beryllia *Beryllium Oxide Properties (solid form) *IARC Monograph "Beryllium and Beryllium Compounds" *International Chemical Safety Card 1325 * National Pollutant Inventory - Beryllium and compounds *NIOSH Pocket guide to Chemical Hazards Category:Beryllium compounds Category:Oxides Category:IARC Group 1 carcinogens Category:Ceramic materials cs:Oxid beryllnatý de:Berylliumoxid lb:Berylliumoxid fi:Berylliumoksidi Category:Beryllium compounds Category:Oxides Category:IARC Group 1 carcinogens Category:Ceramic materials